Thiophosphate esters



Patented July 14, 1953 rnIoPHosrnArE ESTERS Harry W. Rudel, Roselle Park, and Jones I. Wasson, Union, N. J., assignors to Standard Oil Development Company a corporation of Dela- No Drawing. Application March 30, 1949, Serial No. $4,482

This invention relates to addition agents for improving the properties of mineral lubricating oil compositions, and relates more particularly to addition agents which impart detergent and rust inhibiting properties to engine lubricants.

It is known that the addition of certain types of metal organic compounds to lubricating oils improves various properties thereof, such as their oiliness characteristics and their detergent action in engines, particularly manifest in the maintenance of a clean engine during operation. Various metal compounds which have been used for such purposes include the metal derivatives of such organic compounds as fatty acids, naphthenic acids, petroleum sulfonic acids, alcohols, phenols, and ketones. However, these various metal compounds generally have the disadvantage of tending to corrode alloy bearings, such as those of cadmium-silver and copper-lead, now so widely used in automotive engines; and this is especially true in engines which operate at relatively high speeds and high temperatures. It is an object of the present invention to provide a new class of addition agents for oils which are to be used as crankcase lubricants, in which such agents exhibit the desirable properties of promoting general engine cleanliness, improving film strength, reducing ring sticking, piston skirt varnish formation, and the like, and at the same time are comparatively free from a tendency to cause corrosion of metal bearings.

The new class of additives which have been found to meet the above requirements in a highly satisfactory manner are the metal salts of substituted carboxylic acids, in which the substituting group is a phosphite, thiophosphite, phosphate, or thiophosphate radical containing saturated aliphatic or aromatic hydrocarbon groups as substituents for the hydrogen of the acid of phosphorus. The free acids are useful as rust inhibiting additives. More specifically, the new class of additives may be defined by the general formula where R is a saturated aliphatic hydrocarbon radical, saturated cycloaliphatic hydrocarbon radical, aromatic hydrocarbon radical, aralkyl radical, or an alkaryl radical, containing from 2 to 30 carbon atoms; R is a saturated'aliphatic hydrocarbon radical containing from 1 to 20 carbon atoms; X is oxygen or sulfur; M is hydrogen or the hydrogen equivalent of a metal; 111, is 0 or 9 Claims. (Cl. 260-461) 1; and n and p are each a number from 1 to 3. When the above compound contains a metal, the metal may be any metal, but the metals of the alkaline earth metal group are generally preferred. In order that the compound will have sufficient solubility in mineral oil, the total number of carbon atoms in all of the radicals R and B should be at least 8.

Compounds of the above type may be conveniently prepared by contacting a salt, preferably an alkali metal salt, of an acid of phosphorus with a salt, preferably an alkali or alkaline earth metal salt, of a halogen-substituted saturated aliphatic carboxylic acid, at a temperature which will cause a reaction with the formation of an alkali halide, employing as a reaction medium a liquid in which the metal halide is insoluble. The resulting salt of the substituted acid may, if desired, be converted into other metallic salts by double decomposition, or the free acid may be formed and subsequently reacted with a metal or metal oxide or hydroxide. The salt of the hydrocarbon-substituted acid of phosphorus may be formed readily by first reacting an oxide or sulfide of phosphorus with an appropriate alcohol, mercaptan, phenol or thiophenol in a manner well known to the art and then neutralizing the acid thus formed with a metal base. The more" preferred detergent additives are then formed by reacting an aliphatic alcohol with phosphorus pentasulfide, to form a dialkyldithiophosphoric acid, converting this acid into an alkali metal salt, reacting such salt with an alkali metal salt of a chlorinated fatty acid, and finally converting the alkali metal salt product thus formed into an alkaline earth metal salt by double decomposition. Such a product may be defined by the formula where R and R have the meanings defined above and M is an alkaline earth metal.

Among'the alcohols which are generally preferred for use as starting materials in the preparation of the salts of acids of phosphorus, which are in turn reacted with halogen-substituted carboxylic acid salts, may be mentioned ethyl, isopropyl, and amyl alcohols, Z-ethylhexanol, methylcyclohexanol, a commercial mixture of C12 to C16 alcohols, lauryl alcohol, stearyl alcohol, alcohols derived from W001 fat, sperm oil, natural waxes and the like, alcohols produced by the oxidation of petroleum hydrocarbon products,

Oxo alcohols produced from olefins, carbon monoxide and hydrogen, and similar compounds. When compounds having an aromatic group in the phosphorus-containing radical are desired, the starting materials will normally be phenols. Compounds of this type which are suitable for the formation of additives of the present inven-' tion are alkylated phenols, e. g., butyl phenol, amyl phenol, diamyl phenol, tert.-octyl phenol, cetyl phenol petroleum phenols, and the like, as well as the corresponding naphthols.

In the preparation of the salts of halogen-substituted carboxylic acids, any of the saturated aliphatic carboxylic acids containing 1 to 3 carboxyl groups and containing 1 to 22 carbon atoms in the hydrocarbon chain may be employed. The acid may be halogenated in any position in its chain, although the acids containing a halogen in the alpha position are preferred on account of the reactivity of the halogen group in that position. Acids such as acetic acid, propionic acid, butyric acid, capric acid, stearic acid, erucic acid, succinio acid, adipic acid, sebacic acid, trimethyladipic acid, aconitic acid, and acids obtained by the oxidation of petroleum products and of x0 aldehydes are typical of those which may be employed.

The amount of the additives of the present invention which are to be employed in mineral lubricating oil compositions will normally range from about 6.02% to about 5%, and the particular amount in individual cases will be selected in accordance with the requirements of the case and in view of the properties of the base stock employed. For commercial purposes, it is convenient to prepare concentrated oil solutions in which the amount of additive in the composition ranges from 25% to 50% by weight, and to transport and store them in such form. In preparing a lubricating oil composition for use as a crankcase'lubricant the additive concentrate is merely blended with the base oil in the required amount.

The preparation and testing of an example of the additives of the present invention is illustrated in the examples described below, but it is to be understood that the additive prepared and its use in various tests are illustrative only and are not to be construed as limiting the scope of the invention in any manner.

Example 1.Prepamtion of additive A calcium salt of a dialkyldithiophosphate-substituted acetic acid was prepared as follows:

A dialkyldithiophosphoric acid was first prepared by heating a mixture of 456 grams (2 mols) or" the commercial C12-C1s aliphatic alcohol and 111 grams (0.5 mol) of P285 for'two'and one-half hours at 90 C. The product was cooled and filtered to remove a trace of unreacted P285. The resulting acid was diluted with 300 cc. of isopropyl alcohol and converted into the sodium salt by adding a solution of 40 grams (1 mol) of NaOH in 50 cc. of water.

A solution ofsodium chloroacetate was then prepared by' adding 40 grams of "NaOI-I in 50 cc.

of water to a solution of 94.5 grams of mono chloroacetic acid in 50 cc. of water. The sodium chloroacetate solution was added to the sodium alkyl thiophosphate solution prepared as described above, and the temperature of the reactionmixtur e was maintained at 85 C. for two and one-half hours, during which time sodium chloride was precipitated. The product was filtered [(ROhfi S 01120001051 ANALYSIS Sulfur Phosphorus Calcium Theory 4. 7O 2. 28 l. 47 Found 4. 67 2. 37 0.83

Example 2.Laboratory bearing corrosion test A. blend was prepared containing 0.5 weight percent of the additive concentrate prepared as described in Example 1, in an extracted Mid-Continent parafiinic lubricating oil of SAE 20 grade. A sample of this blend and a sample of the unblended base oil were submitted to a laboratory test designed to measure the effectiveness of the additive in inhibiting thecorrosiveness of a typical mineral lubricating oil toward the surfaces of copper-lead bearings. The test was conducted as follows:

500 cc. of the oil was placed in a glass oxidation tube (13 inches long and 2 inches in diameter) fitted at the bottom with a A; inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. 'Two quarter sections of automotive bearings of copper-lead alloy of known weight having a total area of 25 sq. cm. were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing sufiicient agitation of the sample during the test. Air was then blown through the oil at th rate of 2 cu. ft. per hour. At the end of each four-hour period the bearings were removed, washed with naphtha and weighed to determine the amount of loss by corrosion. The bearings were then repolished (to increase the severity of the test), reweighed, and then subjected to the test for additional fourhour periods in like manner. The results are given in the following table as corrosion life, which indicates the number of hours required for the. bearings to lose 100. mg. in weight, de-

termined by interpolation of the data obtained Example 3.Lauson engine test A blend containing 2.0% by weight of the product of Example 1 in a solvent extracted Mid- Continent parafiinic lubricating oil of SAE 10 grade and a sample of the unblended base oil to remove the sodium chloride, and the isopropyl 7 were employed as the crankcase lubricant in tests 5.. with a Lausonengine operating at 295 F. jacket temperature and 300 F. oil temperature, 1800 R. P. M. speed, and 1.5 indicated kilowatt load, the tests being conducted for 25 hours each. The loss in weight of the copper-lead bearing and the varnish demerit were determined in each case. The varnish dcmerit rating was based upon a method of rating in which a perfectly clean piston surface had been given a rating of and a demerit rating of was given to the worst condition which could be expected to exist on that surface. The results of these observations areas follows:

It will be seen from the above data that the additive of the present invention not only exhibited a detergent effect in lowering the varnish formation on the piston surface, but actually reduced the amount of corrosion of the bearing to a substantial degree.

Example 4.Rust test In order to determine the extent to which the product of the invention inhibits rusting in the presence of water, a free acid was prepared by dissolving a portion of the sodium salt product of Example 1 in water, acidifying the solution thus formed with hydrochloric acid, and separating the aqueous layer from the precipitated acid product, and this product was blended in 0.1% concentration by weight in a lubricating oil consisting of a solvent extracted paraffinic turbine oil of 150 seconds (Saybolt) viscosity at 100 F., and the resulting blend was submitted to the ASTM Rust Test D665-47T, which is more specifically entitled Test Method of Tests for Rust Prevention of Steam Turbine Oil in the Presence of Water, Procedure A for Distilled Water. A similar test was applied to the unblended base oil. As a result, the base oil permitted severe rusting of the steel test piece, whil the blend containing the additive allowed only light rustmg.

The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of lubricating oils which have been compounded with such detergent type additives as metal soaps, metal petroleum. sulfonates, metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal organo phosphates, thiophosphates, phosphites and thiophosphites, metal salicylates, metal xanthates and thioxanthates, metal thiocarbamates, amines and amine derivatives, reaction products of metal phcnates and sulfur, reaction products of metal phenates and phosphorus sulfides, metal phenol sulfonates and the like. Thus the additives of the present invention may be used in lubricating oils containing such other addition agents as barium tert.-octylphenol sulfide, calcium tert.-amylphenol sulfide, cadmium oleate, nickel oleate, barium octadecylate, calcium phenyl stearate, zinc diisopropyl salicylate, aluminum naphthenate, calcium cetyl phosphate, barioum di-tert.-amylphenol sulfide, calcium peteroleum sulfonate, zinc inethylcyclohexyl thiophosphate, calcium dichlorostearate, etc. Other types of additives, such as phenols and phenol sulfides, may be employed.

The lubricating oil base stocks used in the compositions of this invention may bestraight mineral lubricating oils or distillates derived from paraninic, naphthenic, asphaltic, or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from Which asphaltic constituents have been:

carefully removed. The oils may be refined by conventional methods using acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced, for example, by solvent extraction with solvents such as phenol, sulfur dioxide, furfural, dichlorodiethyl ether, nitrobenzene, crotonaldehyde, etc.

Hydrogenated oils or white oils may be employed as well as synthetic oils prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products. In certain instances cracking coil tar fractions and coal tar or shale oil distillates may also be used. Also, for special applications, animal, vegetable or fish oils or their hydrogenated or voltolized products may be employed in admixture with mineral oils.

For the best results the base stock chosen should normally be an oil which without the new additive present gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their use also 3 makes feasible the employment of less satisfactory mineral oils or other oils, no strict rule can be laid down for the choice of the base stock. Certain essentials must of course be observed. The oil must possess the viscosity and volatility characteristics known to be required for the service contemplated. The oil must be a satisfactory solvent for the additive, although in some cases auxiliary solvent agents may be used. The lubricating oils, however they may have been L produced, may vary considerably in viscosity and other properties depending upon the particular use for which they are desired, but they usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. For the lubrication of certain low and medium speed diesel engines, the general practice has often been to use a lubricating oil base stock prepared from naphthenic or aromatic crudes and having a Saybolt viscosity at 210 F. of 45 to seconds and a viscosity index of 0 to 50. However, in certain types of diesel engine and other gasoline engine service, oils of higher viscosity index are often preferred, for example, up to '75 to 100, or even higher, viscosity index.

In addition to the material to be added according to the present invention, other agents may also be used such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, organo-metallic compounds, metallic or other soaps, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber olefin polymers, voltolized fats, voltolized mineral oils, and/or voltolized waxes and colloidal solids such as graphite or zinc oxide, etc. Solvents and assisting agents, such as esters, ketones, alcohols, aldehydes, halogenated or nitrated compounds, and the like may also be employed.

Assisting agents which are particularly desirable as plasticizers and defoamers are the higher alcohols having eight or more carbon atoms and preferably 12 to 20 carbon atoms. The alcohols may be saturated straight and branched chain aliphatic alcohols such as octyl alcohol (CsHnOH), lauryl alcohol (C12H25OH), cetyl alcohol (C16H33OH), stearyl alcohol, sometimes referred to as octadecyl alcohol, (C18H37OH), heptadecyl alcohol (C1'IH35OH), and the like; the corresponding olefinic alcohols. such as oleyl alcohol; cyclic alcohols such as naphthenic alcohols; and aryl substituted alkyl alcohols, for instance, phenyloctyl alcohol, or octadecylbenzyl alcohol; or mixtures of these various alcohols, which may be pure or substantially pure synthetic alcohols. One may also use mixed naturally occurring alcohols such as those found in wool fat (which is known to contain a substantial percentage of alcohols having about 16 to 18 carbon atoms) and in sperm oil (which contains a high percentage of cetyl alcohol); and although it is preferable to isolate the alcohols from those materials, for some purposes the wool fat, sperm oil or other natural products rich in alcohols may be used per se. Products prepared synthetically by chemical processes may also be used, such as alcohols prepared by the oxidation of petroleum hydrocarbons, e. g. parafiin wax, petrolatum, etc.

What is claimed is:

1. As a new composition of matter a comound of the formulawhere R is a hydrocarbon radical selected from the group consisting of alkyl radicals, saturated cycloaliphatic radicals, aromatic radicals, aralkyl radicals, and alkaryl radicals, the radicals having not less than 2 and not more than 30 carbon atoms each;.R is a saturated aliphatic hydrocarbon radical containing 1 to 20 carbon atoms; Mis a member of the group consisting of hydrogen and alkaline earth metals; and n is a number from 1 to 2.

2. As a new composition of matter a compound of the formula where R is an alkyl radical of 2 to 30 carbon atoms; R is a saturated aliphatic hydrocarbon radical of 1 to 20 carbon atoms; and M is an alkaline earth metal.

3. A composition according to claim 2 in which R is 4. A composition according to claim 9 in which R is an alkyl radical of 12 to 16 carbon atoms, R is CH2- and M is calcium.

5. As a new composition of matter a compound of the formula -s-prnooon where R is an alkyl group containing 12 to 16 carbon atoms.

6. The process which comprises reacting a mixture of sodium dialkyl dithiophosphates with sodium chloroacetate in the presence of a mixture of isopropyl alcohol and water at a temperature sufiiciently high to cause precipitation of sodium chloride, and removing the sodium chloride, isopropyl alcohol and water from the resulting mixture by filtration and distillation, said dithiophosphates being derived from theproduct obtained by reacting phosphorus pentasulfide with commercial aliphatic, alcohols consisting essentially of a mixture of C12 to C16 saturated monohydric aliphatic alcohols.

'7. A process according to claim 6 in which the sodium dialkyldithiophosphates are reacted with sodium chloroacetate at a temperature of about 85 C. for a period of about 2 /2 hours.

8. The process which comprises reacting the sodium salts formed by the process of claim '7 with calcium chloride in an essentially mineral oil medium, and removing the precipitated sodium chloride by filtration.

9. The process which comprises dissolving the sodium salts formed by the process of claim '7 in water, acidifying the solution thus formed ith hydrochloric acid, and separating the aqueous layer from theprecipitated oily acid product.

HARRY W. RUDEL. JONES I. WASSON.

References Cited in the file of this patent V UNITED STATES PATENTS Number Name Date 2,252,675 Prutton Aug. 12, 1941 2,266,514 Romieux Dec. 16, 1941 2,343,831 Osborne Mar. 7, 1944 2,365,291 Prutton Dec. 19, 1944 2,386,207 Reifi et a1. Oct. 9, 1945 2,494,283 Cassaday Jan. 10, 1950 2,529,304 Mikeska Nov. '7, 1950 

1. AS A NEW COMPOSITION OF MATTER A COMPOUND OF THE FORMULA 